[387067] EARTH: THE WHOLE BALL OF WAX (pp67-70)
A slab of warm paraffin wax is all you need to model the complex structural deformations produced during the rifting of continents. The trick, according to James N. Brune of the University of Nevada, Reno, Nevada, and Michael A. Ellis of the University of Memphis, Tennessee, in a report on p. 22, is to warm the wax from underneath. This creates a temperature gradient that is reflected in the graded behaviour of the wax when strained. The cool wax on top is brittle, but the warmer wax beneath is ductile, a table top analogy of the Earth's crust, which gets more ductile with depth.
The wax models, deformed under conditions simulating various rifting regions, develop faults analogous to those seen in regions of continental extension, but not seen in previous models, based on less realistic solid-fluid (rather than brittle-ductile) transitions. The style of deformation seems to reflect the relative thickness of the brittle and ductile layers, which in the real earth is a function of crustal age and crustal thickness.
CONTACT: Michael Ellis, (901) 678-2007, fax (901) 678-4734; James Brune, (702) 784-4975, fax (702) 784-1833, email brune@seismo.unr.edu.